How to send and receive answers to a web api using ASP.NET C#

Question

I have to call a web API in XML that use EPP (Extensible Provisioning Protocol) and returns a XML as response. I also need to use a certificate to call it, but the received response is null. There is only a sample code in PHP that works.

eppClient.php

<?php 
require_once 'config.php';
require_once 'eppFunctions.php';

//Get XML variable via POST method 
$xmlStr = stripslashes(trim($_POST['xmlStr']));

$response = send_epp_request($USER_CERTIFICATE_FILE, $EPP_SERVER_URL, $xmlStr);

if(!$response === false){

    //Show Server Response as XML
    header("Content-type: application/xml");
    echo $response;

}
?>

config.php

<?php
//Server URL Address For Sending XML
$EPP_SERVER_URL = "api.site.com/submit";

//URL CERTIFICATE FILE
$USER_CERTIFICATE_FILE = "";
?>

eppFunctions.php

<?php 
function send_epp_request_form($USER_CERTIFICATE_FILE, $EPP_SERVER_URL, $xmlStr)
{
    $XML = array('xmlStr' => $xmlStr);

    // create a new cURL resource
    $ch = curl_init();

    //FALSE to stop cURL from verifying the peer's certificate
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    //The name of a file containing a PEM formatted certificate. 
    curl_setopt($ch, CURLOPT_SSLCERT, $USER_CERTIFICATE_FILE);
    //TRUE to return the transfer as a string of the return value of curl_exec() instead of outputting it out directly.
    curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
    //The contents of the "User-Agent: "
    curl_setopt($ch, CURLOPT_USERAGENT, "IRNIC_EPP_Client_Sample");
    //The URL to fetch.
    curl_setopt($ch, CURLOPT_URL,"https://$EPP_SERVER_URL");
    //TRUE to do a regular HTTP POST.
    curl_setopt($ch, CURLOPT_POST, 1);
    //The full data to post in a HTTP "POST" operation.
    curl_setopt($ch, CURLOPT_POSTFIELDS, $XML);

    // grab URL and pass it to the browser
    $response = curl_exec($ch);

    if($response === false) {
        // echo Errors
        echo 'Curl error: ' . curl_error($ch);
    }
    // close cURL resource, and free up system resources
    curl_close ($ch);

    return $response;

}

function send_epp_request($USER_CERTIFICATE_FILE, $EPP_SERVER_URL, $xmlStr)
{
    // create a new cURL resource
    $ch = curl_init();

    //FALSE to stop cURL from verifying the peer's certificate
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    //The name of a file containing a PEM formatted certificate. 
    curl_setopt($ch, CURLOPT_SSLCERT, $USER_CERTIFICATE_FILE);
    //TRUE to return the transfer as a string of the return value of curl_exec() instead of outputting it out directly.
    curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
    //The contents of the "User-Agent: "
    curl_setopt($ch, CURLOPT_USERAGENT, "IRNIC_EPP_Client_Sample");
    //TRUE to do a regular HTTP POST.This POST is the normal application/x-www-form-urlencoded kind, most commonly used by HTML forms.
    curl_setopt($ch, CURLOPT_POST, false);
    //The URL to fetch.
    curl_setopt($ch, CURLOPT_URL,"https://$EPP_SERVER_URL");
    //The full data to post in a HTTP "POST" operation.
    curl_setopt($ch, CURLOPT_POSTFIELDS, $xmlStr);

    // grab URL and pass it to the browser
    $response = curl_exec($ch);

    if($response === false) {
        // echo Errors
        echo 'Curl error: ' . curl_error($ch);
    }
    // close cURL resource, and free up system resources
    curl_close ($ch);

    return $response;

}
?>

What I have tried:

I tried several ways like WebClient, HttpWebRequest or HttpClient, but all of them have no result.

protected string WebApiCall (string Data, string Url)
    {
        //Url in https

        byte[] BytesOfData = Encoding.ASCII.GetBytes(Data);

        string CertFile = Server.MapPath("~/crt/abc.p12"); 
        string CertKey = "abc";
        string ResponseData = string.Empty;

        //ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
        //ServicePointManager.ServerCertificateValidationCallback = (a, b, c, d) => true;
        ServicePointManager.Expect100Continue = true;
        X509Certificate2Collection SrvCertificate = new X509Certificate2Collection();
        SrvCertificate.Import(CertFile, CertKey, X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet);

        //X509Certificate2 SrvCertificate = new X509Certificate2(CertFile, CertKey);

        HttpWebRequest HttpWebRequest = (HttpWebRequest)WebRequest.Create(Url);
        HttpWebRequest.ClientCertificates = SrvCertificate;
        //HttpWebRequest.ClientCertificates.Add(SrvCertificate); 
        HttpWebRequest.Method = "POST";
        HttpWebRequest.Accept = "application/xml";
        HttpWebRequest.ContentType = "application/xml";
        HttpWebRequest.ContentLength = BytesOfData.Length;


        Stream RequestStream = HttpWebRequest.GetRequestStream();
        RequestStream.Write(BytesOfData, 0, BytesOfData.Length);
        RequestStream.Close();

        HttpWebResponse HttpWebResponse = (HttpWebResponse)HttpWebRequest.GetResponse();

        if (HttpWebResponse.StatusCode == HttpStatusCode.OK)
        {
            Stream ResponseStream = HttpWebResponse.GetResponseStream();
            ResponseData += new StreamReader(ResponseStream).ReadToEnd();
            return ResponseData;
        }

        return null;
    }

Answer 1

Try This.

string data = "{}";
WebRequest myReq = WebRequest.Create(url);
 //set webreuqest properties e.g
    //myReq.Method = "POST";
    //myReq.ContentLength =  lenght;
 UTF8Encoding enc = new UTF8Encoding();
 using (Stream ds = myReq.GetRequestStream())
 {
 ds.Write(enc.GetBytes(data), 0, data.Length);
 }
 using (WebResponse wr = myReq.GetResponse())
 {
 Stream receiveStream = wr.GetResponseStream();
 using (StreamReader reader = new StreamReader(receiveStream, Encoding.UTF8))
{

    string content = reader.ReadToEnd();

}
}

Answer 2

Have you checked out this library? https://github.com/CodeMakerInc/EppLib.NET I also found a good step by step article on https://mobtowers.com/2013/03/14/how-to-write-an-epp-client-in-c/